ZNY CTLR EXPERIENCED LOSS OF SEPARATION AT FL210.

Narrative

TFC WAS LIGHT; ROUTINE AND NOT COMPLEX. I WAS LOOKING FOR A RULE IN THE FAA MANUAL 7110.65. I THOUGHT I ISSUED A DSCNT TO THE E145 (ROUTED PSB MIP LVS AVP) FROM FL210 TO FL180. I POINTED ACFT OUT TO A SECTOR THAT THE ACFT WOULD HAVE TRANSVERSED. I INITIATED A HDOF TO LOWER ALT SECTOR ON THE E145 DSNDING FROM FL210 TO FL180 FOR FURTHER DSCNT TO DEST. (I HAD NEVER TAKEN INTO ACCOUNT THAT THE E135 AT FL200 ROUTED J60 WBOUND MAY HAVE BEEN A FACTOR.) I XFERRED COMS TO LOWER ALT SECTOR. I RECEIVED A CALL FROM THE LOWER SECTOR ADVISING THAT THE E145 CALLED LEVEL FL210 VERSUS DSNDING TO FL180. THEY REQUESTED DSCNT; WHICH I APPROVED; STILL NOT TAKING INTO ACCOUNT THE E135. I HAD ACCOMPLISHED AN AUTOMATED HDOF ON THE E135 TO ZOB AS IT WAS ROUTED INTO THEIR AIRSPACE. I ISSUED A COMS XFER TO THE E135 TO CONTACT ZOB. THE E135 READ BACK THE FREQ CHANGE AND THEN ASKED WHAT WAS THE TFC THAT WENT OVER THEM BY 500 FT? I HESITATED AND ADVISED THEM THAT THE TFC WAS AT FL210. NEITHER THE E135 OR MYSELF HAD ANY FURTHER XMISSIONS BTWN US. THE CONFLICT ALERT NEVER 'WENT OFF' ON MY SCOPE NOR THE ZNY OR ZOB MASTER SCOPE. (FOR IF IT HAD; WE WOULD HAVE INVESTIGATED AN OPERROR.) AS I RECALLED THE EVENT TO MYSELF LATER ON A BREAK; I SPECULATED WHAT 'MAY' HAVE HAPPENED. I DID INDEED DSND THE E145 AND THE E145 DID 'BEGIN' THE DSCNT IN CONFLICT WITH THE E135. THE E145'S TCASII ALERTED THE CREW OF THE TFC OR THE CREW NOTICED THE TFC THEMSELVES. THE CREW RETURNED TO FL210 (AFTER DSNDING TO FL205) NOT SURE WHAT HAD HAPPENED OR IF THEY HAD TAKEN THE WRONG CLRNC; THEY DID NOT QUESTION IT. THE CREW OF THE E135 NOTICED THE TFC OR WERE ALERTED BY TCASII; BUT ONLY QUESTIONED IT LATER AFTER DISCUSSING IT AMONGST THEMSELVES. I DID NOT RPT THE INCIDENT TO THE SUPVR FOR I AM UNSURE THAT AN INCIDENT 'ACTUALLY' OCCURRED. I ALSO FEARED RIDICULE/PUNITIVE ACTIONS FROM MY PEERS AND EMPLOYER. I SHOULD NOT HAVE BEEN READING THE MANUAL ON THE POS FOR I WAS OBVIOUSLY DISTR.